The invention relates to an electromagnetic switching system having a coil former made of insulating material carrying a winding, a core which is arranged in an axial cutout of the coil former and forms a pole face with one end on the pole side and is firmly joined to a yoke with one end on the yoke side, an armature mounted on the yoke and forming a working air gap with the pole face of the core, at least one movable contact element that is operatively connected to the armature and at least one counter-contact element fastened on a flange of the coil former on the pole side. In addition, the invention relates to a process for producing such a switching system.
Such switching systems in the form of electromagnetic relays are known, for example, from German reference DE-A-1 639 295 (corresponding to U.S. Pat. Nos. 3,486,142 and 3,524,153) or French reference FR-A-2 341 935. In general, in switching systems of this type it has hitherto been customary to provide a fixed assignment between the coil former carrying the counter-contact elements on the one hand and the yoke on the other hand, the armature also being fixed by means of the bearing on the yoke. The contact force is determined in such systems by the contact follow. That is the additional path which the armature can still travel in the direction of the pole face after the contacts have closed until the stop. Said contact follow, and hence the contact force, has hitherto been set by means of so-called core pole adjustment. In this case the core is pressed into the coil former and with its end on the yoke side into a yoke cutout until it has reached a predetermined dimension with respect to the counter-contact elements. If this pressing in for the purpose of adjustment is performed before the armature and the movable contact elements are put in place, then the adjustment can only be performed on the basis of the dimensions determined, it being difficult to control tolerances. If, however, the core pole adjustment is performed with the armature in place by pressing in the core over the armature, then the latter may be deformed in an undesired manner. If the core is fastened in the yoke by pressing in and notching, high jointing and notching forces occur, which can only be reliably controlled if the core can be pressed into the yoke directly over the core pole face and without any intervening armature. In order to still be able to perform an adjustment of the assembled core even after the armature has been assembled, it has also already been proposed (German reference DE-A-3 148 052) to fasten the core in the yoke by means of a fine thread and to perform an adjustment by rotating the core after the armature has been assembled. However, the fine thread entails additional costly production steps.
An electromagnet is also known already from German reference DE-A-2 226 061, in which resilient detent tongues are provided for fixing the coil foyer on the magnet core in the region of the interior wall of the coil former, which detent tongues are received in a form-locking manner in complementary recesses in the magnet core. However this produces only an insufficient securing with respect to relative displacement of the coil foyer on the magnet yoke, in particular only in one direction. On the other hand, a clamping of the coil foyer onto lugs, not defined in more detail, of the magnet core mentioned therein in the introduction of the description is said to be disadvantageous.
However, even if a precise adjustment was performed between counter-contact elements and core pole face during production, a de-adjustment may occur as a result of aging and concomitant shrinkage of the coil foyer. For example, the coil foyer joined to the yoke can retract in the direction of the end on the yoke side as a result of the shrinkage, with the result that the counter-contact elements are also moved further away from the movable contact elements, that is to say the contact force is reduced. The reliability of the switching system is thereby impaired.